Effects of Substrate Plane on the Growth of High Quality AlN by Hydride Vapor Phase Epitaxy

We investigated the direct growth of c -plane AlN on sapphire (11.0) and (00.1) substrates by low-pressure hydride vapor phase epitaxy (LP-HVPE) without using any buffer, interlayer, or pulsed source supply. The a -plane sapphire was confirmed to be effective for obtaining high-quality AlN with an rms surface roughness of 0.156 nm for 2×2 µm 2 scan and a large crack-free thickness of 3.6 µm. This was partly attributed to the hexagonal c -axis of a -sapphire substrate being perpendicular to the hexagonal c -axis of AlN, leading to the reduced twist degree of AlN. X-ray rocking curves yielded full widths at half maximum (FWHM) of 487 and 636 arcsec for (10.2) and (10.0) reflections, respectively, indicating a low edge dislocation density (reduced twist degree) in the film.